Hand-held, single us unit dose applicators are well known and have been used for decades. In their most generic embodiment they comprise a dual chambered applicator wherein either 1) a frangible dividing wall is formed in a tubular body having a closed end and an open end, which dividing wall isolates the content of the chamber defined by the closed end and the dividing wall from the open end or 2) one or more frangible ampoules is located within the lumen of a tubular body having a closed end and an open end. In use, the frangible element is subjected to pressure to crush the dividing wall or ampoule so as to release and make available for dispensing, the contents therein.
These applicators further comprise an applicator tip having a distal end sealingly engaged with the open end of the tubular body and a proximal end from which the contents of the applicator is be dispensed and applied to whatever substrate is to be treated. According to certain embodiments in the art, the tip may be a porous tip whereby the porosity of the tip itself serves to filter the shards of the dividing wall or ampoule formed when the dividing wall or ampoule is crushed as the contents are dispensed. Other embodiments, especially those wherein the applicator tip is non-porous and relies upon one or more distinct flow paths, typically a lumen or bore along the longitudinal axis thereof, through the applicator tip from its distal end associated with the open end of the tubular body to the face of the applicator tip for dispensing the contents of the applicator, employ a filter element interposed between the applicator tip and the dividing wall or ampoule. The filter element prevents the shards from passing into the lumen of the filter tip and being dispensed with the contents of the applicator.
Over the years, these applicators as well as different elements thereof have been modified, redesigned, and/or reconfigured all in an effort expand their utility as well as their overall performance. Certain of these modifications are dependent upon the specific materials to be dispensed whereas others have broader applicability. Perhaps the most prolific in this regard are the inventors of Closure Medical Corporation. Closure Medical has made improvements in relation to the applicator tips, the integration of a curative in the applicator tip, the use of protective films to prevent the piercing of the container body by shards created by the crushing of an ampoule, and so on, all as will be discussed in greater detail below.
Despite all the improvements to date, there still remain a number of issues with respect to the state of the art applicators, especially as they relate to the dispensing of curable compositions. For example, state of the art applicators either allow for the passage of shards, particularly small shards, of the ampoules or, more commonly, are configured whereby the shards build up on the filter whereby flow of the curable composition past the shard build up is prevented or greatly reduced. In another aspect, the flow of materials is difficult to control due to the pressure needed to force the contents of the applicator through the filter. In yet another aspect, many of the two-part compositions place the second part in the applicator tip or the filter element; however, this results in the initial flow of the first part through the applicator tip or filter element being highly activated while the latter flow is poorly activated, perhaps so poorly that it fails to cure or cures so slowly as to be inappropriate for the given application. Additionally, in those instances which employ a porous applicator tip, it is not possible to place the second component in the lumen of the applicator body as it will inherently saturate the porous applicator tip, if not leak out. Further, the applicators of the prior art have a tendency to introduce bubbles into the composition being dispensed. In compositions having a water-like viscosity this is not an issue since the bubbles tend to break upon emanating from the dispenser tip; however, this is not so for more viscous materials, especially not for curable compositions which are already activated in the applicator and, consequently, whose viscosity is already increasing as it is being dispensed.
Accordingly, there is a need for an applicator having a dual chamber, whether as distinct chambers separated by a frangible dividing wall or as a frangible ampoule within the applicator body or a combination of both, wherein the shards of the crushed dividing wall or the ampoule are not dispensed with the fluid and do not block the flow of the liquid or viscous fluid to be dispensed.
There is a need for an applicator which enables greater control of the rate at which the content of the applicator is dispensed.
There is a need for an applicator of a two-part curable composition which allows for a more uniform activation of the curable composition. In particular, there is a need for an applicator which allows for more uniform activation while also avoiding concerns with respect to leakage or the need for a closure element.
Furthermore, there is a need for an applicator which avoids or at least minimizes the presence of bubbles in the dispensed liquid or viscous fluid composition.